Fire-resistant building covering composition



Feb. 20, 1968 3,369,956

FIRE-RESISTANT BUILDING COVERING COMPOSITION C. C. SCHUETZ ETAL v Filed Nov. 8. 1962 United States Patent O 3,369,956 FIRE-RESISTANT BUILDING COVERING COMPOSITION Clyde C. Schuetz, Prospect Heights, and Richard Ericson, Park Ridge, Ill., assignors to United States Gypsum Company, Chicago, Ill., a corporation of Illinois Continuation-impart of applications Ser. No. 575,475, Apr. 2, 1956, and Ser. No. 356,772, May 22, 1953. This application Nov. 8, 1962, Ser. No. 237,437

1 Claim. (Cl. 161-93) This invention relates to improved building covering compositions and, more particularly, pertains to compositions containing interfelted glass fibers and roofing granules which are highly resistant to the passage of heat. This is a continuation-in-part of our copending application Ser. No. 575,4'75, filed Apr. 2, 1956, now abandoned, which is a continuation-inpart of our application Ser. No. 356,772, filed May 22, 1953, now abandoned.

For many years wood shingles were widely used as roofing materials. The recognized disadvantage of wood shingles, however, is their extreme flammability. Their extensive use continued for a number of years, however, since slate and tile, the only fire-resistant shingles on the market in early times, were expensive and very heavy. A number of years ago, however, the so-called composition shingles were introduced to the market. These are prepared by impregnating a suitable felt with a bituminous saturant, applying to one surface of the saturated felt a coating of asphalt which may or may not have an added mineral filler, and thereafter embedding mineral granules in the asphalt coating. With the introduction of composition shingles which were manufactured for immediate installation at the place of use, the employment of wood shingles has rapidly diminished and, in fact, today wood shingles are prohibited by ordinance in many cities. These prepared asphalt composition shingles are referred to yby the industry as prepared roofing as distinguished from built-up roofing which is formed in place on the surface protected thereby.

The above-referred-to prepared composition shingles are today competitive with Wood shingles in cost and offer very definite advantages in fire protection over wood shingles. It has been appreciated, however, that prior art prepared shingles of this general character, despite the superiority to wood, have only a limited resistance to fire.

A rating system has been devised by Underwriters Laboratories, Inc. to classify various roofing materials as to fire resistance when laid under conditions simulating actual use in the field for the particular roofing material being tested. This rating system and test methods ernployed are set forth in Underwriters Laboratories Subject 55 dated Aug. 26, 1957. This devised system comprises `flame exposure tests, spread of flame tests and burning brand tests. The classification given a roof covering upon being subjected to these tests depends not only upon the manner in which the covering is applied to the roof and the nature of the roof support, but also upon the nature of the roofing material itself. Wood shingles, when laid in courses on a roof, will ordinarily receive no rating whatsoever in the test system devised, While the usual prior art prepared asphalt shingles, when laid in the customary manner, will generally rate in Class C. It is recognized in the roofing art that it is desirable to provide coverings therefor having increased fire resistance which, when applied, will have a rating higher than Class C, that is, Class B or even Class A.

A further development in the lmanufacturing of building-covering compositions for roofing and siding purposes comprises the utilization of glass fibers. By employing glass fibers in shingles and other building-covering ma- Patented Feb. 20, 1968 ICC terials, the fire resistance thereof is greatly improved, as will hereinafter be explained in greater detail.

Glass fibers, however, are filamentous in nature, and when mixed in the loose state with an asphaltic material and subsequently applied to a surface for fire-proofing purposes, there is a tendency for the glass fibers to felt with each other whereby clumps are formed rendering the glass fiber-asphalt mix very difficult to spread. Consequently, in the manufacture of prepared fire-resistant roofing and siding utilizing loose glass fibers, a very serious production problem is encountered.

If the glass fibers are introduced into the asphalt in the form of a thin transparent, lightweight mat, lire resistance benefits afforded by the glass fibers are obtained and the fibers are readily introduced, thus avoiding the disadvantages of mixing and spreading a glass fiberasphalt mix.

It has been found that the introduction of glass fibers in the form of mats in combination with roofing granules in a prepared asphalt roofing produces a startling and unexpected increase in fire resistance, as will hereinafter be explained in greater detail. This increase is much greater than the resistance to be expected from the cumulative fire-resistance effect of these two roofing components.

The use of gravel in built-up roofing or roofing formed -in situ is well known. The use of gravel on fiat or substantially `flat roofs in which it need not all be embedded in the asphalt surface enables any desired amount of protective gravel to be employed. However, on pitched roofs having an elevation greater than three feet per twelve feet of lengt-h, granules employed on the roofing must be fixedly embedded in place in the asphalt to prevent fall-off.

Consequently, prepare-d roofing normally employed on pitched roofs is only able to utilize for protective purposes the amount 'of roofing granules which may be embedded therein; such amount is normally much less than the amount of loose gravel employed on liat roofs.

It `is an object of this invention, therefore, to provide a granule-covered prepared roofing of extraordinary fire resistance employing a glass fiber mat embedded in an asphalt layer.

lIt is another object of this invention to provide a granule-coverd prepared asphaltic roofing which has excellent flow-resistance properties when subjected to direct flame impingement.

iIt is another object of this invention to provide a method -whereby 'glass fibers may be incorporated in granulecovered asphaltic roofing or siding composition in a manner which is both facile and adapted for high speed production.

It is a still further object of this invention to prov-ide an improved fire-resistant covering which is highly resistant to .fiiarne and burn through and is capable of forming shingles which exceed the lire resistance of Class B and in some instances Class A shingle.

' It is a still further object of this invention to provide a method for the manufacture of a fire-resistant covering in which glass Yfibers may be admitted into a bituminous coating in a facile manner without mixing.

It -is an object of the present invention to produce a coating composition applicable to an inherently combustible base sheet material so as to form therewith a prepared, relatively fire-resistant building covering material, such as shingles and sid-ing. The provided covering is :surfaced with roofing granules and contains embedded in the first-applied asphalt coating layer a web or mat of linterfel-ted glass filaments so that if such material be subjected to lire, lthis interfelted `mass will act as a supporting skeleton for the asphalt. Also, both during and after the completion of the combustion, the asphalt will lform in combinations `with .the overlying granules a unique protective sheath whereby to retard penetration of the fire -to underlying stra-ta of the roofing structure.v

The above and other objects of this linvention will become more apparent upon proceeding with the following detailed description when read in the light of the accompanying drawing and appended claims.

The present invention `is definitely to be differentiated from processes an'd products of a somewhat similar nature which have been produced in the past. Such processes have involved, for example, the introduction into the asphalt layer of a prepared roofing of fiow-retarding materials. `Such roofing materials ywere in the form yof roll roofing or cut shingles; various forms of fibrous incombustible material such as asbestos, mineral wool or slag Wool were employed.

The unexpected fire resistance of the prepared building covering composition provided by this invention may be attributed to the combined effect of glass fibers in ma-t form and roofing granules which cooperate to produce la fire-resistant barrier. The mat may be formed by weaving but is preferably formed in a loose random formation in which the glass fibers are gathered into felt. The

mat, however, may be held together with a bin-der if desired, but a loose random formation has also been found to be workable. The fibers should be formed into a unitary mat, and whether the mat is formed by weaving or matting of the fibers is immaterial.

In the formation of the Ifire-resistant covering provided by 4this invention, a roll of paper or rag felt which has been saturated with asphalt, and subsequently cooled, passes through a coa'ter which applies a layer of molten asphalt to the upper .surface thereof. The felted mat of glass fibers is then applied to .the molten asphalt layer. A second coating of asphalt is then applied tto the upper surface of the 4glass mat. The mat may be forced down into the first-applied asphalt coating and the second asphalt coating omitted, or it may be covered by the second asphalt coating, depending upon the desired thickness of `the final covering material to be formed, and depending upon the desired amount of asphalt which is to be included therein. The coated mat is then passed under a 'granules hopper whereat an upper coating of granules is applied to the molten asphalt surface. The resulting mat product is next passed beneath pressure rollers wh-ich force the granules into Ithe asphalt coating. After cooling, the product is ready to be cut into shingles or formed into rolls for building covering purposes. In an alternative method of covering manufacture the glass mat may be deposited directly on the asphalt-saturated felt prior to application of a molten aspha-lt layer.

To reduce the flow of asphalt upon subject the building covering composition to -iire heat, the amount of asphalt applied to the `surfaces of the Iglass fiber mat is preferably maintained at the minimum which -is consistent with desired mat and granule embedment therein. Upon being subjected to fire heat the asphalt products of combustion in combination with the encrusted fiber mat and granules will form a protective blister-like mass which protects the underlying surface.

The glass fiber mat need not be woven but may be formed into a loose matlike configuration, at the site for application `to lthe molten asphalt, by means of a suitable collecting drum which gathers loose fibers by means of suction and deposits a loose-ly formed mat on an underlying asphalt layer disposed on the base of the building covering material to be formed.

For a more complete understanding of this invention reference should now be made to the drawings, wherein:

FIGURE 1 is a cross section of a portion of the finished product of the present invention shown on an exaggerated scale;

FIG. 2 is a diagrammatic drawing illustrating the sequence of steps utilized in the manufacture of the finished product illustrated in FIG. l; and

FIG. 3 is a schematic representation of apparatus which may be utilized for forming a glass fiber mat at the site of application thereof to the base of building covering material to be formed.

Referring now to the drawings, there is illustrated in FIG. 1 a section through a building covering material made in accordance with the present invention. The base sheet 5, consisting of cellulosic fibers such as are commonly used for this purpose, is saturated with asphalt in the well known manner. Applied thereto is a layer 6 of coating asphalt into which there has been introduced a layer 7 of the interfelted glass fibers. There is then a layer 8 of further coating asphalt upon which there is superimposed the layer 9 of roofing granules 10 which are embedded in the asphalt, 'but for the main part extend above the surface of it.

It is to be understood that layers 6 and 8 may be a single layer in which case the fibers will be distributed through the combined layers 6 and 8.

One way of practicing the present invention is illustrated in FIG. 2, it being understood that this is entirely diagrammatical and with no attempt whatsoever to represent the relative sizes of the various equipment or to indicate by more than symbols the apparatus employed.

Referring now to FIG. 2, the numeral 11 designates a roofing felt coming from a roll 12 thereof. The felt is first passed through molten asphalt 13 which is contained in a saturator 14. In the course of passing through the saturator 14 the felt 11 engages roller 15 so as to insure proper penetration of the saturating asphalt through the interstices of the felt 11. The felt may then pass into a usual type of looper 16 through which the saturated felt is carried to allow it to cool and to allow the saturant to equalize in the felt. Molten asphalt 17 is applied from a source 18 whi-ch is provided with the usual control gates, valves, etc., so as to be applied to the felt 11 in the form of a predetermined coating 19. The thickness of the coating or layer 19 may be controlled by means of a doctor 20. The saturating and initial coating operation has been effected by apparatus schematically represented within a bracket in Section A of FIG. 2.

The next process steps in the course of forming the fire-resistant building covering materials of this invention are effected in Section B of FIG. 2. In the particular process modification schematically illustrated, a glass fiber mat is applied to the underlying molten asphalt layer 19 formed in Section A of FIG. 2 by unwinding a suitable mat 21 of interlaced glass fibers from a supply roll 22 onto the molten asphalt layer '19. An additional coating of molten asphalt 17a may be applied to lthe upper surface of the mat 21 from a source 18a; the thickness of this layer may be controlled by a doctor 20a. This asphaltcoating operation is the same as that already described in connection with the coating operation effected by the apparatus illustrated in Section A of FIG. 2. As a result of the two coating operations thus described, it is seen that the glass mat 21 will thus 'become sandwiched between two applied asphalt coatings,

Section C of FIG. 2 illustrates apparatus for applying mineral granules to the building covering as thus far formed. The granules are illustrated as coming from a granule hopper 23 whereby a separate layer 24 of roofing granules is formed on the uppermost layer of the building covering composition. Pressure rollers 25 and 26 will be employed to force the granules partly into the coating whereby their rm adhesion thereto is assured. The rollers 25 and 26 may also be utilized for purposesof pushing the mat 21 into the molten asphalt disposed on the saturated base 11. An excess of roofing granules should be dispensed onto the asphalt 19 (or 17a if a second layer is applied) to assure complete coverage of the upper surface of the moving mat. Excess granules not embedded in the upper asphalt layer may fall by gravity into a collector when the completed covering reaches the end of a supporting conveyor system for return to the hopper 23.

The glass fiber mat 21 may be formed by any suitable apparatus well known in the art. The glass fibers may be air felted or otherwise felted in accordance with any known method.

If desired, the glass fibers contained in the mat may be provided with a suitable sizing of resinous material which will aid in keeping them in contact with each other and which will secure the fibers at their points of mutual contact just as is done in making paper. Such a mat can be made at any point, either in the plant where the operation is carried out, or it may be made elsewhere and shipped in for use. It is, of course, self-evident that the production of such a mat may be carried out simultaneously with the manufacture of the building covering material, the operations being so coordinated that the mat at its proper stage of dryness will be available for incorporation with the asphalt coating 19.

In FIG. 3 apparatus is illustrated which may be employed in Section B of FIG. 2, whereby a loose mat of glass fibers may be formed at the site of mat application to the molten asphalt layer 19 of the building covering composition being formed. The apparatus comprises a hopper 27 which is in communication with a source of loose glass fibers. The loose glass fibers in the hopper are collected by suction on a rotating collecting drum 28 which in the course of rotation forms a thin mat of glass fibers and then deposits the same on the asphalt layer 19 passing therebeneath. Suction is employed in the course of -collecting the glass fibers and in the course of formation of the mat 21a; and is released on that portion of the drum opposed to the molten layer 19. The amount of suction will determine the density of the resulting mat. A binder may also be used in the course of forming the mat.

Referring now more specifically to the glass fibers which are to be employed for purposes of practicing this invention, it has been found that an incombustible inorganic fiber having substantially uniform diameter throughout its length is desired. Drawn glass fibers which are either gas or mechanically drawn were found to be ideal for v this purpose, because these, by being drawn from a plastic or viscid mass of glass, inherently have a substantially uniform diameter. Incombustible fibers, regardless of how formed, each of which possesses a relatively uniform diameter, are intended for use in the mats of the provided covering. Such glass fibers are produced at the present time in enormous quantities and are spun into threads and woven into various fabrics; large quantities are also used in the formation of lightweight insulation mats.

The following examples are presented for purposes of clearly demonstrating the unexpected fire resistance of an asphaltic covering incorporating therein glass fiber mats and granules. The prepared asphaltic coverings discussed hereinafter were subjected to a standard laboratory test devised to simulate a burning brand test for measuring fire resistance. In this test a six inch by twelve inch shingle specimen is placed with its long dimension inclined on an open metal support inclined at an angle of 30 degrees to the horizontal. A two and one-half inch strip of asbestos siding is placed at the lower edge of the incline with the test shingle thereabove. A three and onehalf by six inch piece of asbestos cement siding was placed next to the top edge of the shingle and extended to the top of the incline. A Fisher type gas. burner mounted on a hinged support was lighted and adjusted to provide a fiame with a two inch inner blue cone. Each test was started by impinging the flame at the center of the shingle sample with the burner head one and one-quarter inches from the shingle. The foregoing test is that described on page of our copending application Ser. No. 575,475.

Example 1 embedded in the asphalt layer thereof a glass fiber mat weighing 1.9 pounds per square feet. The asphalt layer was disposed over an asphalt-saturated felt weighing 30.4 pounds per 100 square feet. The glass fibers were coated with .6% by weight of a polyester binder. The fiber mat weighed 2.39% of the Weight of the asphalt employed in the shingle. The mat-containing asphalt layer was covered with No. 11 granules.

Upon being subjected to the above-described test, a flame could be seen through a crack which formed in the back surface of the shingle opposed to the point of fiame impingement after the expiration of fifty-five minutes. The latter time is known as the flame burn through time.

Example 2 The shingle of Example 2 was made exactly as that of Example 1, with the following differences in composition. The shingle weighed only 107 pounds per 100 square feet, and possessed a glass fiber mat employing 14.6% by weight of a resinous furfuryl alcohol binder. The glass fibers in the mat weighed .57 pounds per 100 square feet of shingle which constituted 1.17% of the weight of the asphalt. The shingle of Example 2 possessed a burn through time of seven minutes and twenty seconds.

The above two shingles are to be compared with a typical Class C granule-covered shingle possessing no glass fibers which weighed 103 pounds per 100 square feet. When subjected to the above-described laboratory fire test, this shingle burned through in two minutes and forty seconds.

Additional simulated burning brand tests were conducted on shingles of varying composition-and the results thereof presented in the snbjoined Tables I and II. The individual glass mats employed in the shingles of Table I, with the exception of shingle 16, weighed approximately 1.03 pounds per 100 square feet and contained 14.9% of an organic binder by weight, as revealed by loss on ignition. The glass fibers of the mat body were formed by gas attenuation and had dispersed thereover threads of glass fibers randomly arranged on the body surface. Objects could readily be seen through it.

The glass mat employed in shingle 16, as well as the shingles of Table II, were formed similarly to the above mat except that all fibers were mechanically drawn Textile Type glass fibers. This mat comprised a light layer of fibers arrangedat random with looped threads of glass fiber dispersed over the surface and although objects could be seen through it, the interstices therein were more closely spaced and more uniform than the mat of Table I. The mat of Table II shingles weighed about 1.7 pounds per 100 square feet and possessed about 25.9% of an organic binder, as indicated by weight loss on ignition.

With the exception of shingle 31, which was made with No. 18 granules and shingle 32 which was made with No. 9 granules, all of the granule-covered shingles of Tables I and II were coated with No. 11 granules. These granules conformed to the specification for granules set forth by ASTM, D 312-44, the particle size ranges of the granules employed being presented below:

GRANULE NUMBER Percent n 5 10 Through48 0 2 The above sieve sizes are Tyler standard which will be` recognized as having openings of nominal sizes as'follows: No. 6, 0.132; No. 8, 0,094; No. 10, 0.066; No. 14, 0.047;

'7 No. 20, 0.033; No. 28, 0.023; No. 35, 0.017, and No. 48, 0.012.

In the following tables all times are expressed in minutes and seconds, thus 1:50 is one minute and fifty seconds. All shingles were formed on asphalt-saturated felt weighing approximately 30.4 pounds per 100 square feet. All of the lled coatings of Table I employed 50% by weight of limestone, except shingle No. 14 which only Burn through-flame-time for sample to burn through and flame appear at back.

Tail-distance in inches that material ows down slope from point flame impinges on sample.

Burned area-distance in inches from longitudinal center line of the burner projected onto the shingle specimen to the upper margin of the burned area.

Test is run for sixty minutes or until burn through.

TABLE NO. I

Wt. coating, Wt. coating, Wt. glass Wt. Wt. 100 it.2 Smoke in Burn Burn Length of Length of Shingle no. unfilled filled mat granules shingle back through, through, tail, inches burned glow flame area, inches 3 30.3 61 0:40 3:10 (u) 6 6 4. 30.3 60.1 :34 3:30 5:40 6 6 5 30.3 1.03 63 1:0 6:05 13:40 6 4 6 30.3 31. 5 95. 6 0:53 5:00 6:43 6 4 7 30.3 1.03 60.8 0:50 4:05 14:58 6 3 8 30. 3 1. 03 31. 5 95. 6 1:18 13:38 27:38 6 3 9. 30.3 31. 5 89. 4 0:42 4:53 5:45 6 4 1 30.3 1.03 31. 5 90. 7 1:13 10:33 18:43 5 4 11 30.3 1 03 31.5 95.6 1:10 11:05 26:20 5 4 12 b 30.3 2.06 b 22.9 82.6 1:15 17:18 60+ 2 4 13 b 30.3 d 3 09 b 20.9 89.4 1:30 33:58 60+ 2 4 14 30.3 1 03 31.5 93.5 1:23 15:33 34:45 7 5 15.. b 30.3 3.09 65.6 1:04 25:30 33:55 6 6 16 30.3 1. 7 62.1 1:15 12:20 16:15 6 6 Class C 65. 2 0:48 2:45 4:25 6 6 Bar-Fire e (see note below) 148 2:35 60+ 2 5 Fire-Chex f (see note below) 191 7:00 60+ 3 4 H Flashed and burned in back.

b Insufficient asphalt to properly cover the glass mats and to hold the full amount of granules.

c Contained two layers of the glass mat.

d Contained three layers.

s Bar-Fire is a Class A shingle made by the Barrett Division of Allied Chemical Corporation.

f Fire-Chex is a Class A shingle made by Philip Carey Manufacturing Company.

TABLE NO. II

Simulated Burning Brand Test Wt. of Wt. of Wt. of Wt. of Shingle no. coating glass mat granules 100 sq. ft. Smoke in Burn Burn Length of Length of shingle back through, through, tail, inches burned glow flame area, inches 17 32. 6 1. 7 30.0 94 27 1:50 37:00 52:00 6 4 18.. 35. 0 1. 7 34. 4 103 1:21 40:00 58:00 5 4 19.. 28. 0 28. 2 88. 1 0:50 4:50 6 5 20.. 31. 3 1. 7 63.9 1:15 10:40 5 5 21.. 28. 4 60. 9 0:40 4:00 6 5 22.. 55. 5 1. 7 29. 8 116. 3 1:50 46:20 6 4 23.. 85. 3 1. 7 32. 4 142. 2 2:10 50:00 6 6 24.. 52. 7 1. 7 68. 0 154 1150 51:00 3 4 25.. 31. 5 1. 7 18. 3 84. 3 1210 17:30 5 4 26-. 40. 3 l 3. 4 27. 3 103 1:45 48:00 4 4 27.. 88. 0 h 5. 1 27. 1 153 3:15 60+ 6 5 28.. 67. 7 i 3. 4 51. 0 153 2:45 60+ 6 4 29. 27. 5 i 1. 7 28.0 85.9 1:03 17:15 4 5 30.. 31.0 k 1. 7 28. 6 91.5 1:05 19:00 4 5 31.. 36. 4 1. 7 19.8 92. 5 1:15 21:40 6 4 32.... 30. 6 1. 7 56.0 121. 6 1:20 19:45 4 4 Class C.-- 11%x6 94. 6 1:05 4:25 6 4 Bar-Fire (l) (see note) 125 2:50 60+ 2 4 f1 Contained two mats.

h Contained three mats.

l Formed with an extra overlay over the granules of another layer of asphalt coating containing the mat and surfaced with granules.

had 20% iiller. All of the coatings of Table II contained by weight limestone, except shingle No. 17 which contained no filler.

The weights of the shingles tabulated are those actually obtained expressed as pounds for 100 square feet. The weights of the coating, glass mat and granules are eX- pressed in pounds per 100 square feet; because of the processing steps employed the coating employed may be in error as much as 2.2 pounds per 100 square feet. While a constant glass mat weight is indicated in the tables, there is a slight variance in weight because of the variance in openness present in the mat sections employed.

The multiple mats of shingles 12, 13 and 15 of Table I were applied separately while the multiple mats of shingles 26 and 27 of Table II were stapled together before inserting in the coating.

In the following tables the various expressions employed therein are dened as follows:

i Mat was applied next to the felt before adding the coating.

k Ihe mat was placed on top of the coating before adding the granules.

l Bar-Fire is a class A shingle made by the Barrett Division of Allied Chemical Corporation.

It may be seen from the above tabulated results that a shingle (3) weighing 61 pounds per 100 square feet had a glow burn through time of three minutes and ten seconds. The presence of a limestone iiller in the asphalt (shingle 4) increased this time a mere twenty seconds. However, the presence of a glass mat in the asphalt (shingle 5) increased the glow burn through time substantially to six minutes and ve seconds, whereas adding 31.5 pounds of roofing granules to the composition of shingle 3, as was done in shingle 6, merely increased the glow burn through time to ve minutes.

When both granules and a glass mat were added to the composition of shingle 4, as was done in shingle 14, the glow burn through time increased from three minutes and thirty seconds to fteen minutes and thirty-three seconds. The increase in ame burn through time is even more dramatic, increasing from five minutes and forty seconds in shingle 4 to thirty-four minutes and forty-five seconds in shingle 14.

The effects on fire resistance of a prepared asphalt shingle afforded by granules and glass bers in mat form are also apparent from Table II. Shingle 21, having neither granules nor glass fibers, had a glow burn through time of four minutesv and a ame burn through time of six minutes and forty seconds. When granules were added to substantially the same composition as shingle 21 (shingle 19) the times increased to four minutes and fifty seconds and seven minutes and fifty seconds, respectively. The presence of both granules and glass fibers in shingle 25 provided a glow burn through time of seventeen minutes and thirty seconds and a flame burn through time of thirty-four minutes; it will be noted that shingle 25 weighed less than shingle 19.

The above test results provide evidence of the following facts. The use of limestone filler in the asphalt provided no apparent beneficial result. However, the addition of surfacing granules alone to the shingle composition increased the tire resistance somewhat, but not significantly. The addition of a glass mat to an asphalt shingle alone approximately doubled the shingle burn through time.

The addition of both surfacing granules and a glass ymat to an asphalt layer of a prepared rooting greatly increased the burn through time of the roofing. The improved results in fire resistance resulting from the combination of both glass and granules is totally unexpected from the improvement afforded by each alone. Although the specific reason Vfor such unexpected increase in fire resistance is not known, it is theorized that a unique crust is created by the glass and granules which combines w-ith the asphalt products of combustion to effectively shield the lunderlying surface to be protected from fire heat or fiame impingement.

Theabove tabulated data also reveals facts which are to be expected, such as increased fire resistance with increased asphalt thickness (com-pare shingles 18, 22 and 23). The use .of two or more mats markedly increases fire resistance (compare shingles 10, 12, 13, 26 and 27). As is also noted yfrom the latter shingles, multiple mats may be applied separately or stapled together and applied as a unit. The use of three mats (shingle 27) enabled a shingle to have the fire resistance o-f a Class A shingle.

As noted from the data set forth in connection with shingle 28, mats applied as an overlay gave better results. As may be seen by comparing the data relating to shingles 29 and 30, placing the mat directly on the felt base before applying the coating did not give as satisfactory results as a mat placed over the c-oating. Placing the mat between two asphal-t layers which was the normal procedure employed with the remaining shingles utilizing mats appeared to be the best method of fabrication.

The foregoing tabulated results clearly display the unusual fire resis-tance properties of granule-covered prepared rooting having included therein an asphalt layer in which is embedded a lightweight glass fiber mat.

In Table I `the average diameter of the fibers employed in the mat body was about 16 microns. These fibers were gas drawn. The average diameter of the fibers making up the surface threads of the Table I mats was about 9.5 microns; the latter fibers were mechanically drawn. The fibers making up both the body and surface threads of the mats employed in Table II were mechanically drawn. The body fibers had an average diameter of 24.5 microns and were filter-grade fibers. The fibers employed in the surface threads had an average diameter of `20.5 microns. The fibers employed in the mats of Examples 1 and 2 were gas drawn and had average micron sizes of about 11-16 microns. While any available glass fibers can be used, it is preferred to use as small a fiber diameter as possible in order to obtain the maximum area to weight lratio.

By incorporating the fibers as a 4felt it is possible to add the fibers only to the butt portion as it is the only part of the shingle directly exposed to the ame and thereby effects a substantial saving in fiber. This is not as readily possible when the `fibers are mixed in with the asphalt before applying to the felt. It is desirable, however, to extend the felt beyond the butt portion somewhat to assure adequate fire protection.

The glass fibers need only comprise at least about 1% by weight of the asphalt; the multiple mats may, of course, be employed. As noted from the above tables, the granules generally comprise at least about from 1l8% by weight of the shingle. The granules should be adequate in number to afford a substantially continuous coating for the prepared rootting asphaltic layer. The asphalt should be sufficient in quantity to have the glass rnat completely embedded therein and the granules completely surfacing the same thereby enabling the above-described unique blister to form upon being subjected to fire heat. In the appended claims the term asphalt is to be construed as encompassing within its scope those bituminous compositions normally employed in roong of the type disclosed.

Without further elaboration, the foregoing will so fully explain the character of our invention that others may, by applying current knowledge, readily adapt the same for use under varying conditions of service, while retaining certain features which may properly be said to constitute the essential items of novelty involved, which items are intended to be defined and secu-red to us by the following claim.

1. A prepared roofing of improved fire resistance comprising a rooting base, a prepared-roofing coating asphalt layer disposed on said base, a preformed open integral mat of glass fibers of substantially uniform diameter embedded in said coating asphalt layer; said fibers comprising at least about l percent by weight of said coating asphalt layer; mineral roofing granules embedded in the upper surface of said prepared roofing so as to provide a substantially continuous roofing covering; said granules comprising about 18 to 45 percent by weight of said roofing and having a particle size of between about .0l to .-13 inch; the coating asphalt being present in quantity sufficient to completely envelop said glass mat and have each of said roofing granules adhered thereto.

References Cited UNITED STATES PATENTS 1,436,914 11/f1922i Seigle 161-158 2,702,069 2/ 1955 Lannan 264-116 2,695,257 111/1954 Castellani 156--71 X FOREIGN PATENTS 5 04,9711 5 1939 Great Britain.

OTHER REFERENCES Miller, In Place of Felt Fiberglass Mat, article in ll-GF American Roofer for December 1946, pp. 12, 13, 25, 2'6, and 27.

Owens-Corning Fiber Glass Bulletin No. 12B-1,

Built-Up Roofs, RW 3, A1, April 1952-including 

1. A PREPARED ROOFING OF IMPROVED FIRE RESISTANCE COMPRISING A ROOFING BASE, A PREPARED-ROOFING COATING ASPHALT LAYER DISPOSED ON SAID BASE, A PREFORMED OPEN INTEGRAL MAT OF GLASS FIBERS OF SUBSTANTIALLY UNIFORM DIAMETER EMBEDDED IN SAID COATING ASPHALT LAYER; SAID FIBERS COMPRISING AT LEAST ABOUT 1 PERCENT BY WEIGHT OF SAID COATING ASPHALT LAYER; MINERAL ROOFING GRANULES EMBEDDED IN THE UPPER SURFACE OF SAID PREPARED ROOFING SO AS TO PROVIDE A SUBSTANTIALLY CONTINUOUS ROOFING COVERING; SAID GRANULES COMPRISING ABOUT 18 TO 45 PERCENT BY WEIGHT OF SAID ROOFING AND HAVING A PARTICLE SIZE OF BETWEEN ABOUT .01 TO .13 INCH; THE COATING ASPHALT BEING PRESENT IN QUANTITY SUFFICIENT TO COMPLETELY ENVELOP SAID GLASS MAT AND HAVE EACH OF SAID ROOFING GRANULES ADHERED THERETO. 